text:
When filing an ICAO flight plan with LPV, is marking GNSS equipment necessary or redundant?
Should equipment 'B' (LPV) and Equipment 'G'(GNSS) both be filed simultaneously in an ICAO flight plan, or does equipment 'B' simply imply GNSS?

You should fill both G and B.
If I understand the last row of the official ICAO guidance correctly, field 10 (equipment code) of the flight plan must contain at least B and G if you want to fly LPV approaches:

(cropped from ICAO Guidance for the provision of NAV/COMSUR information in the New ICAO 2012 Flight Plan)
You will also have to enter "NAV/ SBAS" in field 18.
This is also confirmed by the following information on the ForeFlight support page:

When specifying a PBN code, be sure to also specify R (Code for Performance-Based Navigation (PBN) Approved) and the associated sensors that the PBN code requires. For example, PBN Code D2 is RNAV 1 using GPS, therefore Equipment Code G (GNSS) must also be specified.
[...]
These tables are a general aid for entering filing codes in ForeFlight and are not an authoritative or comprehensive equipment specification. Consult the AFM or AFM supplements for your aircraft to determine which codes are actually appropriate before attempting to file using ForeFlight. The codes listed below are in addition to the other ICAO Equipment code that may be appropriate for your aircraft.
WAAS

GNS 430W - R, B, and PBN B2, C2, D2
GNS 530W - R, B, and PBN B2, C2, D2
GNS 480 - R, B, and PBN B2, C2, D2
GTN 6XX/7XX - R, B, and PBN B2, C2, D2
GPS 175 - R, B, and PBN B2, C2, D2
GNX 375 - R, B, and PBN B2, C2, D2
G1000, 2000, 3000, 5000 WAAS - R, B, and PBN B2, C2, D2

(foreflight.com, emphasis mine)


text:
Where can I obtain a .KML file for a TRACON’s area of responsibility?
I want an overlay on my moving map for the radar service areas of a TRACON facility.  Are there any sites that host this for free?

Related, although no accepted answer

SE GIS and/or Open Data may be of assistance.

As I don't like double posting, you might want to have a look to my answer on the same question that @Pondlife linked. Please note though that the provided format is AIXM, not KML

@SteliosAdamantidis, AIXM is extension of GML and converting that to KML should be fairly easy (selecting which polygons to extract will be the harder part).

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

sort: votes


text:
Is a CFI's 1st-time pass-rate based on the student or the instructor's first attempt?
This question doesn't apply to anything I have done personally, and beyond word-of-mouth, I have no references about this happening.
Some people claim that if an instructor endorses a student and they fail an FAA check ride and then a different instructor endorses the same student for the re-take and then the student passes the re-take, that the instructor who endorsed the re-take may count this on his or her record as a first-time pass since the student passed on the first attempt for that instructor's endorsement.
The intended benefit of recording this would be utilizing it for CFI renewals and gold-seal CFI applications.
Is this a practice that is considered to be acceptable to the FAA?

I believe that your pass rate is based upon your number of students who passed on their first attempt after endorsement vs the number of students you endorsed for the checkride.  I don’t believe the FAA makes any other distinctions here, at least not for §61.197 requirements for the renewal of a flight instructor certificate nor for 89001, Section 13, Issuance of a Gold Seal Fight Instructor Certificate.

Yes, it definitely answers the question.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
How does a failed turn and slip indicator behave if the gyro isn't spinning at all?
I have my own theories, but I have never experienced a turn coordinator or turn and slip indicator's gyro failing first-hand.
If the gyro isn't spinning, would the instrument behave like a weak accelerometer but on a different plane of movement, or would it just do nothing at all?
For example, would the weight of the motionless gyro of a turn and slip indicator resist movement laterally when the plane is rolled and cause a momentary turn indication from roll or are the centering-springs strong enough to overcome virtually any inertial resistance offered by the weight of the gyro?
Another way of asking this is if you held a turn and slip indicator unit in your hand with the display window facing your palm and you rotated (rolled) the unit side-to-side rapidly in sort of a door knob turning motion, would the turn rate indicator needle tilt at from the center position on the display at all?

It depends on how it fails, there are lots of possibilities on what caused it to stop spinning and they can all lead to different outcomes. In this instance it just kind of bobbed around as if it were free floating. But if something is jamming the mechanics it may simply stop moving altogether so it really just depends on how it fails.

Turn coordinators have a number of failure modes because they are normally electrically powered and depend on very precise gyro RPM, so the gyro motor runs on fixed frequency 115v ac and there is a teeny tiny static inverter in the unit to convert the airplane's 12 or 24 vdc power to fixed frequency a/c for the motor.  If the motor's not running so the gyro is stationary, there will be indications from gyro's mass inertia as the housing moves, but it will be quite random and the needle will randomly tilt and move around.
Because they are sensitive to bank, Turn coordinators also use an internal damper in the gyro mechanism to filter out small movements.  The electric gyro can keep running, but if the damper fails, and it is bumpy at all, the airplane symbol will dance all over the place and you really can't use it (I had one go bad like this, where the gyro still worked but the indicator became hyper-sensitive and moved constantly with the slightest motions of the plane, making it pretty much as unusable as one with the gyro failed).
So for an electric turn coordinator, the main failure modes will be an electrical failure in the inverter or a/c motor driving the gyro, failure of the internal damping system, or failure of the bearings.

Dave is right in that there are different failure modes that could cause your turn coordinator to behave in different ways. However your ball-in-a-tube slip/skid indicator will not be affected by the failed gyro, and will continue to work.

"However your ball-in-a-tube slip/skid indicator will not be affected by the failed gyro, and will continue to work."-- !!   Unless gravity fails.


text:
What is the relationship between the EASA and JAA?
I have heard of two different European aviation authorities: EASA and JAA (or JAAT).
What is the difference in their functions?  This would include things such as:

Whether they are somehow part of the same organization, but are referred
to separately (such as the FAA and NTSB both being US government agencies).
One being the parent organization of the other.
Whether they are separated by which countries they oversee within Europe.
Whether they issue separate licenses/certificates.
Whether one is an older version of the other similar to the CAA being the predecessor to the FAA.

Does this answer your question: https://aviation.stackexchange.com/q/1210/19

This question seems much more detailed & specific than the suggested duplicates. Voting to leave open.

@DeltaLima Yes, mostly.  It is semantically accurate to say one is the predecessor to the other or not really?

Yes, I guess one can say that, especially for the EU member states. Note that each EU member state still has a CAA, which has the responsibility to, amongst others, issue and revoke flight crew licenses. But they follow the EU and EASA directives and guidelines to do so. So when we talk about an EASA Pilot License, it typically is a license that is issued by the CAA of one of the EU Member states, in accordance with EU regulations.


text:
Where is there an FAA source that states that squall lines are non-frontal?
There's a question in the FAA commercial question bank that indicates that squall lines are nonfrontal, and the reference for the question points to the Aviation Weather Advisory Circular.
The word, "nonfrontal" (or any variation of it ie "non-frontal") does not appear in that document.  Also, the word "squall" appears four times, and none of those seem to have information that indicates that they are nonfrontal.
Where is the FAA providing this information?  Is it actually correct?

Errors on FAA questions would be par for the course.

If you go back and look at the previous version of that AC, AC-006A, the index has this definition:

squall line - Any nonfrontal line or narrow band of active
thunderstorms (with or without squalls).

I guess that the question in the question bank was based on AC-006A, which was current until 2016. As for today, chapter 12 of the PHAK has a slightly different definition (p.12-23). It says that squall lines are not necessarily frontal:

Squall Line
A squall line is a narrow band of active thunderstorms. Often it develops on or ahead of a cold front in moist, unstable air, but it may develop in unstable air far removed from any front.

If you need more detailed information on squall lines and fronts you may get a better response on earthscience.SE.


text:
Does the FAA consider flights that generate content for profitable YouTube channels displaying airborne video to be commercial operations?
Is there any guidance from the FAA such as an Advisory Circular, Letter of Interpretation, or other document that directly clarifies the scenario below?
If a pilot creates aerial video content while acting or logging as pilot-in-command and profits from advertising revenue through a service such as YouTube on which that video content is hosted, would that cause the flights during which the videos were recorded to be considered commercial operations by the FAA?
Note: Videos made by costs-shared-pro-rata passengers are not within the scope of this question.

Closely related, maybe a dupe?

@Pondlife definitely related, but reading that question, I think you could probably justify changing its title to, "Could operating a camera while acting as a required crew member be considered reckless behavior?"  If it did encompass the meaning of my question, I would be inclined to label the other one as being overly-broad.

The answer here is, potentially yes, but it depends.  In the United States the Federal Aviation Administration casts a wide net out over all kinds of activity it sees a potentially commercial in nature.  Former FAA lawyer Kathy Yodice wrote an AOPA article on what the FAA considers compensation or hire activity.  Unfortunately, the answer is not always clear; the FAA sees compensation as virtually anything of value and often just “knows it when they see it”.  Yodice writes:

Certainly, compensation comes in the form of any payment of money, but it also includes those instances when no money is made on the flight or when the payment isn’t even enough to cover all of the expenses.  The simple exchange of money to reimburse all or some of the expenses like fuel, transportation, lodging, or meals is usually enough. Compensation can also take the form of accumulation of flight time. Compensation can be good will or the expectation of future business. It could be the effect of furthering one’s economic interest or the prospect of a return favor. Something of value paid or given to a third party could be considered compensation if it is conditioned on the operation of the aircraft. For now, the FAA’s policy is to draw the line at considering charitable deductions of costs as compensation:  “Since Congress has specifically provided for the tax deductibility of some costs of charitable acts, FAA will not treat charitable deductions of such costs, standing alone, as constituting ‘compensation or hire’ for purposes of the regulations.” But, that is about the only exception we’ve seen in practice.  Otherwise, if you get something for taking the flight, the FAA is likely to call it compensation; if, in fact, you get nothing, you won’t have run afoul of the regulations.

So could a private pilot run afoul for making money on YouTube for flying videos?  Possibly.  Essentially YouTube is brokering an arrangement between content creators and advertisers and videos are ‘something of value’ to advertisers.
But here’s the catch.  In the above scenario, you are not directly exchanging your ability to pilot an aircraft for something of value; you’re simply out flying an aircraft.  Recording the flight is just incidental to it.  Editing, publishing and then selling the footage for compensation is something you’re doing on your own time and not related to your flying.
Another caveat is that §61.113(b) states that a private pilot may act as PIC for compensation or hire if:

(1) The flight is only incidental to that business or employment; and
(2) The aircraft does not carry passengers or property for compensation or hire.

Now in the YouTube scenario, a professional content creator’s business is content creation, not flying and the flight was only incidental to the person’s primary business.  It’s similar to an FBO employee and private pilot asked any his supervisor to ferry an airplane from the main office to a satellite airport for use there by the business.  Here the employee, even though a private pilot, many fly for compensation or hire as the flight was only incidental to the business.
Now let’s take a scenario where, say a content creator and private pilot gets numerous requests from social media subscribers to shoot a particular location from the air or the performance of specific maneuvers or demonstrations of the aircraft.  In this case we begin to get into a gray area where the overlap of exchanging airmanship for something of value starts happening.  It becomes even more suspect if the persons making the request are authorized representatives of the firms which advertise on this pilot’s social media channel.  Potentially an overzealous FAA inspector could cite you for flying for compensation or hire.
Again it all depends.  For more information on this subject I would consult an attorney who operates specifically in aviation law.

The FAA has answered the meaning of §61.113 through an Advisory Circular, legal interpretations and NTSB cases.
AC 61-142 Sharing Aircraft Operating Expenses in Accordance with 14 CFR §61.113(c)
The FAA uses four criteria to determine if a flight was a commercial operation

The holding out or willingness to
transport persons or property
from place to place
for compensation or hire.

7.1.3 In assessing whether a particular operation involves common carriage,
the FAA has consistently interpreted § 61.113(c) to mean that a
private pilot have a common purpose with his or her passengers and to
have his or her own reason for traveling to the destination.7 The U.S.
Court of Appeals for the District of Columbia Circuit affirmed this
interpretation and recognized the FAA’s “common purpose test” as a
limitation on the expense-sharing provision of § 61.113(c)

8.1 Compensation is the receipt of anything of value that is
contingent on the pilot operating the aircraft; i.e., but for the
receipt of the compensation, the pilot would not have taken that
flight. Compensation does not require a profit, profit motive, or the
actual payment of funds. Reimbursement of expenses, accumulation of
flight time, and good will in the form of expected future economic
benefits can be considered compensation. Furthermore, the pilot does
not have to be the party receiving the compensation; compensation
occurs even if a third party receives a benefit as a result of the
flight.

9.2 Destination. In assessing whether a pilot is operating consistently with the expense-sharing provision, the FAA considers
whether the pilot has his or her own reason for traveling to the
destination. When the pilot, not the passenger, chooses the
destination, it suggests that the pilot is not simply transporting
passengers for compensation. The common destination satisfies the
common purpose test even if the pilot and the passengers have
different business to conduct at the destination. For some time, the
FAA has indicated that, in order for a common purpose to exist, the
pilot must have his or her own personal need to fly to that
destination, i.e., his or her own particular business to conduct at
the destination. Therefore, when the pilot has no particular business
to conduct at the destination or the flight is only for the purpose of
transporting passengers, no common purpose exists. The common purpose
test can be stated as “but for the receipt of compensation, the pilot
would not have taken that flight.”

Aren't those four criteria to differentiate common vs private carriage rather than commercial vs. non-commercial operations?  The spirit of the question would be if a pilot is a private pilot holder rather than a commercial, would generating revenue as a byproduct of their flights make it a commercial operation.  I think I failed to make it abundantly clear that this would be a private pilot or lower grade holder in my hypothetical scenario.
Pipeline patrol operations do none of those four things (other than be for compensation or hire I suppose), but they are commercial.


text:
How would a pilot apply the information found on a 500 Millibar Vorticity chart to a flight?
The U.S. Flight Service website has these weather products listed:

I have circled the 500 Millibar Vorticity Charts.  I've been a pilot for 10+ years and have never heard mention of this chart by anyone in aviation.  I am wondering why is it listed here, but no one seems to use it.
What purpose does the information it provides serve for pilots?

My understanding is that it shows the Isobars of atmospheric pressure at around the 18000 foot MSL altitude. It will show pressure gradients, low pressure and high pressure zones of the atmosphere at the altitude that demarcates where 50% of the atmosphere resides below. It’s main purpose is to indicate horizontal and vertical spin of air mass movement due to ridges and troughs of atmospheric pressure, wind shear, and the corialis force. This gives a good indication of the upward movement of rising air, energy being infested by a thunderstorm, and how much of spinning force is being applied to a storm to increase its risk of growing to dangerous levels.
Typically, other aviation weather tools would point a pilot to a no-go flight decision way before reaching this one. Some pilots may use it for limited applications (like glider pilots using the skew-t/log-p diagram). This chart can be a useful tool for meteorologists and meteorology enthusiasts to come up with reports of broader scope. You will see it mentioned in Area Forecast Discussions.


text:
Why is a right pattern the standard for a hold?
Why are right turns the standard hold turning direction?  Why not left?  Is there a reason or is it arbitrary?

It might be helpful if we could find out when standard holding procedures were first introduced. In civil aviation, they seem to have appeared in the late 1940s or early 1950s, but I believe the basic procedure goes back long before that.

This is a total shot in the dark. And, I have no citations for this. I always assumed that the a left-hand traffic pattern and a right-hand hold for a missed approach put the aircraft on the same side of the extended runway centerline. Presumably, this would be a more “protected” side of the airspace. Since standard traffic patterns for fixed wing aircraft are left, that would make the holds to the right.
Although, AOPA says the following...

“Many holding patterns are executed in VFR conditions, which means that those in a holding pattern could encounter opposite direction VFR traffic that might be climbing or descending through the holding altitude. Veering to the right (as required by right-of-way regulations) to avoid opposite-direction traffic keeps the holding aircraft in its pattern. This would not be true when executing a left-hand hold, which is why left patterns are the exception, established only when necessary (because of terrain, for example).”
https://www.aopa.org/news-and-media/all-news/2017/may/01/ifr-fix-what-were-they-thinking


text:
What official government document should a pilot check to determine what magnetic north a VOR was set to when it was commissioned?
Today I learned that VOR stations are all set to magnetic north at the time of commission, and since magnetic north moves, the VOR is not necessarily in-line with magnetic north in the present.
Where can a pilot look to read numerically what the VOR is set to as its magnetic north?  I understand a sectional chart could be measured, but I want to know where I can read the setting in a manual.
For example, is it contained in chart supplements?

Are you asking about the FAA?

The chart supplement does list the magnetic variation of the VORs. Looking under the "radio aids to navigation" section for a nearby airport, it's listed at the end of the line, right after the elevation.

BATTLE GROUND (H) VORTACW 116.6 BTG Chan 113 N45º44.87´ W122º35.49´
  160º 9.6 NM to fld. 253/21E.

Another source is the radio fix and holding data records from the FAA. Among other information, you can find the magnetic variation in the remarks section, along with the year it was set.

REMARKS:
  ...
  BTG MAG VAR 1975/E21

It's not official, but the easiest place I've found to get this is to search for the navaid on AirNav.


text:
How could a turbocharger experience over-boosting due to cold oil?
How can cold oil cause a turbocharged engine's automatic waste gate to stick, leading to over-boosting?
Diagrams I've found online for waste gates don't appear to indicate a connection between it and cylinder oil.

The wastegate system uses engine oil pressure to drive the wastegate actuator, and this oil pressure is metered to the actuator by a controller that senses manifold pressure and throttle position and admits more or less oil to the actuator to drive the wastegate butterfly valve, to achieve the manifold pressure commanded by the throttle opening.
The responsiveness of the control system is sensitive to oil viscosity.  When the oil is cold, the controller and actuator is sluggish and laggy because of the thick oil, which can lead to overboosting when the throttle is opened quickly and the wastegate is unable to keep up, resulting in excess flow through the turbine and excess boost.

Is this applicable to all turbochargers or is this method just one of several and this particular one is one that uses engine oil, while others do not?  The example you present above: is this purely mechanical, or is it digital?

No this is a traditional mechanical turbocharging system and is still pretty much what you will see on most piston engines even today although maybe the latest designs are going with digital/electrical control.  If the manual for the airplane has the admonition you mention about cold oil, it'll be this type of system.  These engines still use a Bendix mechanical fuel injection system designed in the 50s.  It's a very conservative business because simple and reliable and easy to fix is the priority.  Solid state magnetos are out there but have only been around for about 20 years.

Notice the flow to the actuator comes from the oil COOLER.  On a very cold day this oil may be more viscous before the engine warms up.  An actuator oil temperature gauge may be in order.


text:
Is it a violation to list an alternate airport based on an approach your aircraft is not equipped to execute?
A pilot has planned a flight to another airport, and the weather indications at the destination require an alternate airport to be included in the flight plan.  An ILS and a VOR approach exist at the selected alternate airport with standard alternate minimums. The airplane to be flown is not equipped with an ILS glide slope indicator, but it has a VOR.
If the weather at the alternate airport at the estimated time of arrival to that  alternate airport is indicated to be a 700 foot ceiling and 3 miles of visibility is this pilot in the above hypothetical situation violating a regulation by filing that alternate airport?
Another way to word this question is, does the approach that the selection of the alternate airport is based on actually have to be an approach the aircraft is equipped to execute?
Based on the regulation wording in §91.169 this is unclear.  Do any relevant letters of interpretation exist?  Otherwise, can you please provide some written evidence to support an answer on this point?
I have emphasized some of the wording pertaining to how this ties in with a flight plan below in the related FAA regulation.  Nowhere in this wording does it say anything about the aircraft having to be able to actually execute any of the approaches mentioned, only that they're "published for that airport".
I am asking this because it seems contrary to common sense ADM, yet it does not appear to be prohibited.
§91.169(c) IFR flight plan: Information required.

(c) IFR alternate airport weather minima. Unless otherwise authorized
  by the Administrator, no person may include an alternate airport in an
  IFR flight plan unless appropriate weather reports or weather
  forecasts, or a combination of them, indicate that, at the estimated
  time of arrival at the alternate airport, the ceiling and visibility
  at that airport will be at or above the following weather minima:
(1) If an instrument approach procedure has been published in part 97
  of this chapter, or a special instrument approach procedure has been
  issued by the Administrator to the operator, for that airport, the
  following minima:
(i) For aircraft other than helicopters: The alternate airport minima
  specified in that procedure, or if none are specified the following
  standard approach minima:
(A) For a precision approach procedure. Ceiling 600 feet and
  visibility 2 statute miles.
(B) For a nonprecision approach procedure. Ceiling 800 feet and
  visibility 2 statute miles.

I have not found any LOI's that cover this specifically but a broad interpretation of

§ 91.205 Powered civil aircraft with standard category U.S. airworthiness certificates: Instrument and equipment
  requirements.
...
(d)Instrument flight rules. For IFR flight, the following instruments
  and equipment are required:
...
(2) Two-way radio communication and navigation equipment suitable for
  the route to be flown.

Once can broadly say that if you intend to fly an ILS (alternate or not) 91.205 requires suitable equipment i.e. an ILS receiver and CDI capable of displaying as such.

To put it another way you could say he can only take credit for that alternate if the forecast meets on the non-precision alternate minima since his a/c can only do non-precision approaches.

@JohnK sure.  That's common sense.  Where is it written?

Seriously, does everything need to either be specifically allowed or specifically prohibited?  Have we lost our ability to discern intent?  You know what the intent is here, right?  If you had a mishap as a result of filing for an alternate where the mins were below what your equipment was capable of, would you feel comfortable explaining your decision making process to the NTSB?

@RyanMortensen "equipment suitable for the route to be flown" is clear enough for me since the "route to be flown" could include the trip to the alternate.  I don't think that requires too much legalistic parsing of language in this case.

Michael and John: well stated, both of you!

And don't forget the general regulation on "careless or reckless" operation of aircraft.

I'm not at all suggesting anyone should.  I'm also not ignoring the existence of other topics for which similar fine points are clearly stated in regulation even though common sense would suggest it as obvious.  I wonder why they treat it differently here.


text:
When did the FAA begin offering added-rating tests for flight instructors?
I don't recall there being abridged versions of the knowledge test for added CFI ratings when I earned my initial CFI certification such as AIF(flight instructor instrument added rating), and back then I would have had to have taken the full FII(flight instructor instrument initial CFI certification) test.
I could have simply forgotten since 2009.
When did the FAA begin offering added-rating flight instructor knowledge tests?

In the question above, the missed point is that the abridged tests are for category changes.  So an instructor who was only an airplane CFI or who held no instructor certificate with an instrument rating in any category would need to take the full exam for the desired category to add the instrument instructor rating, but for example, a helicopter CFII who was only a fixed-wing CFI who wanted a fixed-wing CFII added to his fixed-wing CFI certificate would only need the AIF(shortened version) for fixed-wing because he already holds an instrument instructor rating in a different category.

Could you decode your abbreviations for us. I just took all of the tests and I am not familiar with those abbreviations.
Just to clarify for those who are not familiar with the knowledge tests. You need to take the Fundamentals of Instruction knowledge test (FOI) for all of the instructor certificates. You can take the Basic Ground Instructor (BGI) test, Advanced Ground Instructor (AGI), and Instrument Ground Instructor (IGI) if you want to get a Ground instructor certificate. To get your CFI certificate you need to take the Flight Instructor Airplane (FIA) test. CFII requires the AIF. There are separate tests for Sport Pilot Instructors.
If you are adding a rating to an existing certificate, you can take an abbreviated version of the test, e.g. if you already have your CFI Airplane, then you can take the add-on test for gliders and only have to answer 25 questions rather than 100, and the questions will focus on glider operations assuming you already know the rest of the stuff.
Once you have any instructor certificate, you never have to take the Fundamentals of Instruction test again.
I don’t know when the short tests started, but if you look at Order 8080.6D which was published in 2003, you can see that short tests were available then. Since you had your CFI in 2009, you had the option of taking an abbreviated test for your CFII.

It's possible to get your initial cfi with FII. Not all cfis would take the FIA. Same for glider, helicopter, etc. as initial CFI.  Not to be rude, but none of this answers the specific question posed.

@RyanMortensen Your question wasn’t particularly clear, but if the question was, "When did the FAA allow short knowledge tests for an add-on rating?", then the answer is, as I said in the post, prior to 2003.


text:
Are flight schools required to verify citizenship of all students?
Is the requirement to confirm citizenship and provide a logbook endorsement required for those who already hold a pilot certificate?
Does another instructor's prior endorsement that confirms citizenship was verified act as a substitution for subsequent instructors, or does each instructor need to check and make their own endorsement verifying citizenship no matter what? This is with the assumption that there are multiple freelance CFIs rather than a flight school employing many CFIs who take turns teaching the same student.
If no, would that not imply that each flight review with a new instructor would need a new citizenship verification or are currency checks exempt?

You are required to verify the identity of people undergoing initial Sport Pilot, Recreational Pilot, Private Pilot, Instrument, and Multi Engine training.  Any other kind of dual instruction does not require verification of US citizenship or TSA approval of resident aliens.  See 49 CFR 1552.3(h).
The CFI must inspect the original documents and verify they are authentic.  The CFI must endorse the CFI’s own logbook with an endorsement per AC 61-65 indicating they have done such and verify the student is a US Citizen.  These records must be kept for a minimum of 5 years.  If the CFI cannot validate the student as a citizen, be done, they must submit the student’s information and immigration documents to the TSA and with for their approval prior to beginning flight training.
https://www.aopa.org/advocacy/pilots/alien-flight-training-program/us-citizens-seeking-flight-training

I see a requirement to keep original records for five years, but nowhere do I see 65. Was that a typo?


text:
How much water does it take to cause a flameout in a modern turbine engine?
Turbine engines such as the PT6 that have inertial separators have a reputation for being able to deal with intake water very well.  How much can they handle?  Do the manufacturers torture-test their engines to see how they will operate under wet conditions such as heavy rain?
Of reciprocating, turboprop, or turbojet engines, which type handles large volumes of water most effectively?

While it doesn't answer the specific question, there's plenty of video that demonstrates the testing:  https://www.youtube.com/watch?v=faDWFwDy8-U

As an example, a GENX engine is tested to ingest 3 tons of water a minute. I found a truly painful to watch video that gives some extreme weather highlights of a GENX engine (https://en.wikipedia.org/wiki/General_Electric_GEnx). Video:  https://www.youtube.com/watch?v=_PR0Ka_J2P4

Wow, @gwally, painful indeed!

When you're running in heavy rain, you put continuous ignition on, so you can have flameouts and relights almost immediately, and the only way you'll know is little fluctuations and spikes in hot section temperatures.

@gwally, I was expecting it to be painful to see engines getting destroyed, but this is painful on a whole other level

Turbofans are the best at taking in a large volume of water. Almost all of it stays in the bypass stream, as it's deflected away from and around the core's inlet. Most turbofans are designed to Part 121 requirements, calling for reliable operation at 20 g/m^3 of water, well beyond typical rain conditions.
As an example, when an A380 had its engine control wires cut, it took 2 hours for the fire crews to drown the engine (page 9 on paper, 19 pdf). Of course, a dip in water would've done that easily, but it's next to impossible to get that much rain.
20 g/m^3 is about the equivalent of delivering about 300 gpm (20L/s) of water into a large jet engine's airflow. That's two fire lines, but not all of the water gets in. This is the amount where the engine is certified to work, drowning it takes more.
A related question goes into more detail: How does a jet engine handle suddenly entering a lot of rain?
Turboprops also deflect the flow of water in flight around the spinner. Some rely on inertial separators, used at takeoff, landing, and in the clouds, for better protection. Turbojets don't have that feature, but haven't experienced a lot of flameouts in practice.
Piston engines also avoid taking in water by having their intake face forward or below rather than above. They're no different from road cars, which also run fine in the rain.
But that applies to ordinary rain that falls on the ground. Conditions in low-altitude clouds, especially on the edge of freezing, can be considerably worse. Reliable operation of piston engines in such is not certain and not recommended.

Reviewing this later, I'm wanting to confirm that "20 g/m^3" is "20 gallons per cubic meter".  20 US gallons would be about 8% of a cubic meter.

@RyanMortensen It's just grams. While this seems low, clouds typically have less than 1 g/m^3. 20 g/m^3 is about the equivalent of delivering about 300 gpm (20L/s) of water into the engine's airflow,  assuming at all gets in.

You may wish to start by looking at a maximum amount of rain possible per given volume of air.  Then evaluate air flow into the turbine, as any circular motion will tend to sling droplets to the side.
As turbines do not run anywheres near stoichiometric ratio, water intake generally will not affect the burners enough to either deprive them of oxygen or heat.  Water expands to steam at a ratio of 1 to 1600.  Using 20 g water per
meter$^3$ as a test criteria, evaporating rainwater in the compressor would change the air composition from 20 parts per million water to:
20 ppm × 1600 steam volume/liquid water volume = 32,000 cubic centimeters of water vapor, or around 3%.
Add on another 20 g per meter$^3$ to account for high relative humidity and you have roughly 6 % water vapor to 94 % nitrogen/oxygen atmosphere entering the combustion chamber.  Plenty of oxygen to burn fuel.
Since water vapor requires more energy to raise its temperature than dry air, fuel consumption increases slightly.  Water vapor being lighter than air reduces mass flow, but water in the compressor intake will increase density by lowering temperature increase during compression.
Even in torrential rains, total moisture content is not enough to significantly affect the operation of the turbine.  Hurricane hunters routinely fly through the worst of tropical downpours unscathed.
Interestingly, a reciprocating (piston) engine with a turbocharger will be less affected than an naturally aspirated engine under these conditions, as the turbocharger compression will help prevent icing by heating the intake air.

I did not see any modern turbines among the hurricane hunters.  They are mostly old turboprop aircraft.

@AnonymousPhysicist  these turboprop engines are ingesting whatever the storm can throw at them.  The "old" hunters have the structural strength designed in to handle the weather (provided they are checked for fatigue and corrosion).

In the last paragraph, I believe you mean "a turbocharger will be less affected than an naturally aspirated engine".


text:
Are airplanes on skis considered to be the land or sea category?
If an airplane is on skis, would that fall under the airplane single/multi engine land categories based on the fact that they operate on land, or would it be considered more closely related to sea categories due to handling characteristics such as a lack of disc brakes?
Would landing on snowy ground vs frozen bodies of ice such as a frozen lake make any difference to the answer?


text:
What is this small number on the top right of an IAP?
I've looked in the instrument procedures handbook, and I cannot locate a reference for what this 5-digit number on the top right above the approach name is.
What is this number, and what does it mean?

Related

Would it have been that hard to write it 2019-06-20 instead? It has all the same properties (strictly monotonically increasing, same lexicographic ordering) and uses only twice the amount of space (technically, less, since the hyphens are narrower than a digit), but is much clearer.

@JörgWMittag There is also ISO ordinal date format, which would yield: 2019-171, which is a standard format, and more likely to be recognisable than what is there.

@GregoryCurrie: That would indeed at least make it clear that it is a date. Still requires mental gymnastics to actually figure out how old the revision is.

@JörgWMittag Well, in some cases more, some cases less. Given two of these reports, it's trivial to determine the number of days between them.

Honest question - I don't know the answer, @JörgWMittag, does it really matter how old the revision is? If you're looking at two copies, it's very easy to determine that 18254 is older than 19171, thus 18254 should be thrown out as no longer accurate/current. There's no guarantee that 19171 is still current (the newest release), but it's newer and that's the important thing, no?

So which chart would be more recent? 2020-05-04 or 2020-04-05 ? The answer depends on your personal background not on the chart itself, and that makes it ambiguous, and that makes it dangerous. Year and day of year is simple and does not involve parsing the date string and it doesn't matter if the user can parse the date string as long as they know it is just an issue number.

@PaulSmith Except that yyyy-mm-dd isn't a personal preference, it's an ISO standard, ISO 8601. Which also contains the ordinal date (yyyy-jjj) format mentioned above. As a human factors person, the format I have always preferred -- which isn't an ISO standard -- is 2020-MAY-05. In either English or French, nearly everyone can grok it with minimal mental processing.

@grumpy1arrival - I didn't say it was preference, I said it was your background. My background, and apparently yours, is y-m-d or d-m-y, but our cousins almost always use m-d-y.  That and the fact that it requires any parsing at all is what rules it out.

It is the year followed by the day of the year of the last ammendment to the chart. If there have been no changes to the chart since it was first issued, this space is blank. In this case the chart was revised on the 171st day of 2019. If you look at the bottom left hand portion of the chart, the date shows the last time the procedure was revised e.g.—17AUG17. Apparently there were changes to the chart (obstacles,  name of the airport, typos in the notes, etc.) that did not affect the procedure, so the dates are different.
Refer to the Aviation Chart User’s Guide.

The Date of Latest Revision is shown on the top margin above the
  procedure title. The Date of Latest Revision identifies the Julian
  date the chart was last revised for any reason. The first two digits
  indicate the year, the last three digits indicate the day of the year
  (001 to 365/6).
The FAA Procedure Amendment Number, located on the left bottom margin
  below the City, State, represents the most current amendment of a
  given procedure. The Procedure Amendment Effective Date represents the
  AIRAC cycle date on which the procedure amendment was incorporated
  into the chart. Updates to the amendment number and effective date
  represent procedural/criteria revisions to the charted procedure,
  e.g., course, fix, altitude, minima, etc.


text:
When outbound from an IAF on an approach to a procedure turn, may the pilot choose whether to use time or distance?
I was trained that if a fix to be flown over and then outbound for an approach is off-airport, then fly out for 1 minute prior to making a procedure turn.  If it is over the airport, then fly outbound for 2 minutes instead of 1.
Would it also be proper to simply decide on a minimum distance to be flown such as 5NM outbound from the fix as long as it is within the published maneuvering area for the procedure such as 10NM from the IAF?
I know the times are only guidelines, but basically, what I am asking is would not using time at all and simply using DME as the guide be considered improper procedure?
Here is an exemplary approach to add something tangible to this question. It has an off-airport procedure turn with a requirement to remain within 10NM.

Using DME only is perfectly acceptable the FAA does not actually specify how exactly to execute the procedure turn but where and at what altitude. This is covered in the AIM:

5-4-9 Procedure Turn and Hold−in−lieu of Procedure Turn. A procedure turn is the maneuver prescribed when it is necessary to
  reverse direction to establish the aircraft inbound on an intermediate
  or final approach course. The procedure turn or hold−in−lieu−of−PT is
  a required maneuver when it is depicted on the approach chart, unless
  cleared byATC for a straight−in approach. Additionally, the procedure
  turn or hold−in−lieu−of−PT is not permitted when the symbol “No PT” is
  depicted on the initial segment being used, when a RADAR VECTOR to the
  final approach course is provided, or when conducting a timed approach
  from a holding fix. The altitude prescribed for the procedure turn is a
  minimum altitude until the aircraft is established on the inbound
  course. The maneuver must be completed within the distance specified
  in the profile view. For a hold−in−lieu−of−PT, the holding pattern
  direction must be flown as depicted and the specified leg
  length/timing must not be exceeded.

The guidance is pretty straight forward that you need to be at the prescribed altitude and within the "remain within" distance but the type and execution of the maneuver is largely up to the PIC as they go on to elaborate.

On U.S. Government charts, a barbed arrow indicates the maneuvering
  side of the outbound course on which the procedure turn is
  made.Headings are provided for course reversal using the 45 degree type
  procedure turn. However, the point at which the turn may be commenced
  and the type and rate of turn is left to the discretion of the pilot
  (limited by the charted remain within xx NM distance). Some of the
  options are the 45 degree procedure turn, the racetrack pattern, the
  teardrop procedure turn, or the 80 degree, 260 degree course reversal.
  Racetrack entries should be conducted on the maneuvering side where
  the majority of protected airspace resides. If an entry places the
  pilot on the non−maneuvering side of the PT, correction to intercept
  the outbound course ensures remaining within protected airspace. Some
  procedure turns are specified by procedural track.These turns must be
  flown exactly as depicted

The standard 1 minute timing is a convenient way to execute the maneuver for light aircraft since 1 minute at approach speed is usually ~1.5 miles (assuming a 90 Kt maneuver/approach speed) and will often keep you in the protected area.
Depending on how you read the regulation in reality a pilot may only use distance, although you may use time as an estimate and helper to execute the maneuver.

In other words left or right also doesn't matter? Regardless of the barb? In the exemplary procedure turn, could I pilot go right to 051 as well as left to 051?

Just to be clear, I am talking about after the outbound PT heading 231 then making the turn to 051.

@RyanMortensen my apologies I mis read, yes you are free to turn in either direction technically although the FAA does publish suggested maneuvers which will dictate a right turn. The risk you run with a left turn is coming in wide and intercepting past the IAF.


text:
Does the FAA generally consider a door opening in an unpressurized cabin during flight to be an emergency?
Sometimes doors pop open on older training aircraft during flight.
I've read some indications from poorly-documented sources suggesting that this is considered an emergency, but it doesn't appear to be addressed in any flight manuals, the AIM, or the FARs.
Is there any publication from the FAA that indicates a stance on the issue as it pertains to it being considered an emergency or not?

I've had it happen many times, never declared an emergency nor filed an ASRS. After the third time in the same aircraft I did have some choice words for the A&P though.

The question contains a misconception - the FAA is not the arbiter of what is and isn't an emergency.

That is true, but they are allowed to hold an opinion on anything they want to.

Of course it's an emergency - that's why everyone jumps out of the open door and pulls their rip cord (eventually)!

A door popping open in a GA aircraft is not considered an emergency. I have not seen it in the FAR/AIM. I don’t have a POH in front of me. If memory serves me correctly, the POH for a 2015 and later Piper Archer has this event listed under the category of Abnormal Procedures. There is a separate category for Emergency Procedures. On the checklists for three different aircraft models from my former flight school, it was also listed under Abnormal. Although the checklists are less than official documents confirming this event’s status, they  definitely point to it not being an emergency.
Like the previous poster, I have had doors open during flight. It has always been a non-event. The doors tend to be designed with the hinges positioned on the leading edge of the door. This keeps the door from flying fully open in the aircraft’s slipstreams. One instructor actually demonstrated the effects of alternately opening the doors on a Cessna 172 to induce yaw. You have to apply a considerable bit of force to swing the door fully open at 90 knots.
Conversely, only half of the Robinson and Loach helicopters I have flown have had the removable doors in place. And, most of the smaller skydiving planes in which I have flown have been unmodified, regular GA planes with the seats removed. Some of them had the right door removed, also, and were still able to achieve 17,000 feet. Opening the door (or in some cases, the tail) does not seem to adversely affect performance enough to classify it as an emergency.

A door popping open is not an emergency in itself, it has to cause a threat to the safety of the flight or those on the ground to be an emergency. I've had doors pop open in a light aircraft in flight and it has been a non-event every time, I didn't mention it to ATC as there was no reason to, I just told maintenance once I was on the ground. I've never seen a FAA or other country authority publication saying it was an emergency.
Regs generally don't get that specific, what is life threatening on one airplane may be a non-event in another. The POH and airplane specific training is typically where emergency events are specified.

Likewise.  Have you seen anything that addresses it at all?  If it is addressed somewhere, but they don't treat it as an emergency, then that's enough to suggest to me that it is just a low-risk occurrence.  Every time it has happened to me, it has also been no big deal; we just shut the door again and move on.

See my edit @RyanMortensen.

It really depends on the aircraft. In most certified light piston training aircraft it's a non-event as described in other answers. In the Lancair 320/360 and Legacy which have forward-hinged canopies instead of side doors, and have much higher wing/tail loading than the typical trainers, it can be quite deadly. Beyond the pilot distraction factor, the aircraft becomes difficult to control due to the disrupted airflow over the tail and oscillations of the canopy angle, forward visibility is substantially reduced, and the pilot has to take some actions that are not necessarily intuitive (increase speed, do not try to land immediately, do not try to close the canopy, go to altitude to practice handling, then go to a very long runway and touch down at much higher speed than normal).
https://www.lancairowners.com/sites/www.lancairowners.com/files/wp-content/uploads/Legacy-Canopy-Safety-Issue-27-April-2014.pdf
I'm not sure whether a certified aircraft with a similar characteristic would be approved; perhaps with a reliable warning system to prevent takeoff with the canopy improperly latched.


text:
What protection did the Concorde have against an uncontrolled decompression?
The Concorde's cruising altitude was 60,000 ft. I believe if the cabin ruptured at this altitude, everyone onboard would be almost instantly killed, if not from the Armstrong limit then from hypoxia (as oxygen masks cannot supply sufficient oxygen at that altitude).
Therefore, there should have been extra protection against cabin decompression in the Concorde. This type of accident would have probably caused an immediate stop to the Concorde program.
What safeguards did the Concorde have against an uncontrolled decompression?

Why would it need extra protection compared to other planes? Pressurisation problems are extremely rare as it is, rapid decompression even more so.

Are you asking about a near instantaneous explosive decompression (I think you are since you mention "cabin rupture") or some other failure in the pressurisation system?  It makes a big difference to the answers.  E.g. Concorde could lose 2 windows entirely and still maintain a cabin altitude of 15,000 feet, whilst cruising at 60,000 feet indefinitely.

I guess all airliners are at the same level of safety in case of rapid depressurization: they need to go down to a safest oxygen partial pressure. Descending with a delta wing can be done at a higher rate (12,000 / 15,000 fpm) as explained in the linked pages, but anyway 15 minutes of oxygen in the pax masks seems a large margin and pilots already wear their masks. See on PPRuNe, here // and // here. Ironically, the only accident for Concorde occurred during takeoff, on the ground.

If you have an explosive decompression at mach 2; either it was caused by a rapid disassembly of your plane; or it will probably be followed by it within seconds. Pressure just became one concern on a the many concerns you now have.

This is the main reason why Concorde had such small windows. It was calculated to reduce the rate of decompression to a survivable level in case one window fails. (The prototype, by the way, had much larger windows).
Other than that, I don't know of any other 'special' decompression mitigation measures that would be unique to Concorde.
There were, of course, things that had to be done in a very special manner on Concorde in case of decompression. For example, rapid emergency descent: there was a special program that transfered fuel forward during emergency descent. It could be activated by a single button, and the flight engineer had to keep the program up to date for the current flight conditions. (Generally, keeping the CG/fuel balance was pretty much a full time job for the Concorde flight engineer). But this would hardly help in case of 'uncontrolled' (explosive) decompression.

I hope I corrected that typo in the intended way!

Concorde could lose an entire window and the pressurization system could maintain cabin pressure without loss of compression.

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text:
Why do solar planes have many small propellers instead of fewer large ones?

Many solar planes, like NASA's Helios (pictured above), NASA's Pathfinder, and to a lesser extent Facebook's Aquila employ the use of many small motor propeller sets instead of one or two engines like most planes. Why is this?
Smaller motors tend to have slightly higher power density, but aren't the relative losses higher on the smaller airfoils of these propellers?

Related question about why having many small engines usually isn't the right thing. (Which doesn't contradict this question or its answer.)

Related

Because they are very lightweight and fragile. Therefore, thrust and propulsion mass must be distributed over span - a single, large propeller and motor would put too much force into the structure locally. Also, it would require a higher landing gear to give the larger propeller the required clearance.
You are right about the higher losses. However, these airplanes were built to reach record altitudes, and wing loading must be as small as possible to make that possible. Also, boundary layer problems on propellers are less severe than on wings because the rotation will cause the slowed boundary layer to be moved outwards from centrifugal forces. There the blade moves faster which will very effectively suppress flow separation.

Conventional commercial designs try to maximize kg-kms per dollar fuel cost or kg payload per dollar investment. Or minimize operating & maintenance cost.
All these goals need an economy of scale that forces few large complex turbines.
On the other hand, most solar planes focus on raw, dollar-agnostic performance / endurance metrics like max height or max range etc.
This is an entirely different optimization problem.
Also, with higher payloads of conventional designs the structural weight of a sturdy airframe is already a sunk cost. With solar planes your baseline airframe can be very slender so every strengthening is adding weight.
Another fundamental aspect is that in solar the generation is anyways distributed & not centralized. Electrical distribution is relatively easier vs mechanical transmission.
In a conventional design it is difficult to get distributed generation (many tiny turbines & even if you did the fuel distribution system would offset any advantages) & no easy way to transmit mechanical power to multiple props unless you add a mechanical-to-electrical generation system.
PS. A lot of this is speculation on my part based on your very interesting question. I could be wrong.

You're certainly right about heat engines in general (and turbines specifically) being the less efficient the smaller they are.

Don't forget the electrical advantages of multiple motors. No need to conduct all the current to a single place with long lengths of heavy wire, no need to control a large current. Also, many small motors and propellers provide redundant depth/graceful degradation in case of a failure(s).

would the wiring really be that massive to matter?

Are engines lighter than wires???

@MobyDisk You didn't take into account the weight ratio of large to small engines. The proper question should be: Are many small engines lighter than a single massive engine + wiring. The answer: I have no idea. I would very much like to know this myself.

In addition to the thrust distribution, a multi motor design also allows you to turn off some motors if you run into a cloudy situation that provides too little power.  One long bus tying all the panels together and each motor connected to it allows all the power to flow to a subset of motors.  Once the sun comes back out, you turn all the motors back on and speed up.
This comes from living on a boat powered by solar panels and seeing just how powerful clouds are at turning 1KW panels in 200W panels.  Being able to pare back the drain on the batteries is the only way to survive the "brown out".

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
Why did the F-14 sweep wing control have a cover?
I learned from Top Gun maverick that the F-14 had what seemed to be a metal cover in front of the wing sweep adjustment cursor. Maverick modifies the sweep angle twice, and twice needs to first lift the cover, then actuate the sweep angle control.
It seems to be a very clunky interface to me. What's the purpose of the cover, and why was it designed that way?

During normal operation the wing sweep angle is controlled automatically by the CADC.
The manual override would only be in use in case of CADC malfunction or on the ground to "oversweep" the wings over the horizontal stabilators.
The manual override control is in fact protected by a guard in order to prevent accidental usage/activation (similar to other critical switches in the cockpit), which makes sense considering how close the lever is to the throttles (The yellow-black-striped "slider" to the right of the throttles).


text:
Why were rotary vane compressors never used in jet engines?
It seems like a rotary vane compressors have ideal characteristics for a jet engine. They can generate high pressure ratios (up to maybe 10-12) compared to older axial compressors and I think they can have a high flow rate at ~90% energy efficiency. They also seem simpler to construct/cheaper than axial compressors.
I understand that modern axial compressors can generate a higher pressure ratio, but historically why didn't rotary vane compressors have a place over at least centrifugal compressors in earlier jet engines?

The most important characteristic for a jet engine compressor is high mass flow rate with light weight and if possible small size. For the same size, the flow rate can be increased by operating the compressor at higher rpm. But sliding components don't allow that.
Only the axial and centrifugal compressors can achieve sufficient flow rates, so they are used. Centrifugal compressors achieve higher pressure ratio for weight, but are larger, so they were used in many early designs and now remain in small turboprops while larger engines use axial compressors for their compactness.


text:
Do any subterranean runways exist for airplanes?
Are there any examples of runways that are under the cover of some terrain such as a runway built into the side of a mountain as a tunnel, perhaps with an entrance and an exit on both sides to facilitate go-arounds?
I could see advantages to this for national security purposes because of the natural protection from kinetic and explosive attacks provided by rock.
For example, I've spoken with Mormons who boasted that the Granite Mountain Records Vault could take a direct hit from a nuclear weapon and still remain intact.
I consider it a truism that any surface-based airport would be obliterated by a nuke.
I recognize that such a facility may not be declassified, but barring that, if they don't currently exist to public knowledge, is this something that would be reasonably possible to build?

Your description reminded me of visiting the Aeroseum in Sweden, which is a "nuclear-bomb-proof aircraft cavern built under a 30 meter thick rock massif". But only the hanger is in the mountain, the runway is outside, so it does not qualify...

Allegedly plenty of them in N. Korea. Called "thunderbirds runways".

The closest thing I can think of is Pilatus Aircraft.  Their factory and hangars were to be blasted into the side of Mount Pilatus.  This would  protect them during WWII, but no mention of the runways being included in the subterranean construction. https://www.flyingmag.com/pilatus-whole-new-light/

@mins that's an answer.  Pretty much exactly the kind of design I was thinking of.

While one may protect the runway itself and the planes parked along it, bombing the heck out of the entrance would likely close it enough to make it unusable. Dropping a nuke in the general vicinity would do likewise. Sounds like a great concept for science fiction or a James Bond movie, but totally impractical in reality.

@FreeMan: Good remark, but what if they also built underground airways, which I suggest to name underways?

@mins: Also, instead of using wings to keep them off the ground, we could put them on something called "wheels" which run on steel "tracks".

@mins I could see the utility in training straight-and-level flight.

@mins The photo in that article appears to show underground hangars but an open runway.

@StephenS: Yes, the article also says: "This taxiway may in fact be an auxiliary runway". But 1/ I'm very skeptical this is useful and thus exists, 2/ There are a lot of articles about runways, random one: "North Korean military engineers are completing an underground runway beneath a mountain that can protect fighter aircraft from attack until they take off at high speed through the mouth of a tunnel"

http://ausairpower.net/APA-2011-01.html shows some of the problems and advantages of even underground hangars. Seems even the Chinese, with seemingly limitless military budget and workforce, aren't into building underground runways.

For takeoffs, maybe... But for landing? No! What if you miss the entrance?

"G-CD going around at one zero feet on a very tight deadside..."

There have been rumors in the fringe media that North Korea was building an underground runway near the Southwest region of Wonsan in Kangwon Province, but that was 13 years ago and I couldn't find confirmation that it had been completed. The runway, which was to run northeast to southwest, was supposed to be paved in cement and run through a mountain through a 30-meter wide entrance. Aside from that, apparently no one has been crazy enough to try that.


text:
Is it true that as of 2014, flight reviews are waived for current flight instructors under FAA rules?
I'm assuming this is false, or I wouldn't be asking...
Just the other day, another flight instructor in my local area, whom I know, told me:

"... new rule as of 2014: if you keep your CFI current, you don't need
  a flight review!"

This is in regards to the FAA system.
I couldn't find a source for that, and I have never heard this before.
I am aware that a requirement to have one hour of ground instruction as a part of the flight review is waived for current CFIs, but I have never heard that the flight portion is waived as well.
My flight review is coming up, so it has been almost two years since I have personally received a flight review, which was in 2014.  I'm just wanting to verify this information and receive a source if it is true.

In 2014, passing a practical test for a flight instructor certificate or rating constituted a flight review.  Before that date, it did not.

It is false.
14 CFR §61.56(f) states:

A person who holds a flight instructor certificate and who has, within
  the period specified in paragraph (c) of this section, satisfactorily
  completed a renewal of a flight instructor certificate under the
  provisions in §61.197 need not accomplish the one hour of ground
  training specified in paragraph (a) of this section.

Also, AOPA has some great input on this topic:
"Pilot's Guide to the Flight Review"
Bottomline: You are correct, your friend is not.
Maybe there was a misunderstanding in the conversation whereby they were specifically talking about their own certificate (and any ratings they may be seeking that may take place of the flight review) as opposed to a general term?

I don't think this is a misunderstanding.  I asked him to fly with me for a flight review and that quote was from a text he sent me back.  I'm going to  discuss this with him now.  Thanks!

FYI: This is what confused him.  He missed the "practical test" part, and I convinced him he was incorrect.  What actually changed is that CFI practical tests now qualify to replace the need for a flight review, but before they did not.


text:
Why there is such a strong correlation between the range of an airliner and its passenger capacity?
Why we rarely see an A320 (or equivalent aircraft) on a long route with all premium business seats or an A380 (or equivalent aircraft) with high density seating and on a short route?
On top of that, it is a much easier task to design a long range light aircraft and a short range heavy/high capacity aircraft, so why have no airliners (as far as I know) ever been designed with these characteristics in mind?

You should clarify whether you are interested in the correlation between range and seat density, or range and number of passengers. The title and the body of the question are not consistent, unless you assume high number of passengers means high seat density (which could be true).

Strongly related, possible dupe here

@mins true there is an ambiguity in my question but I am not quite how to remove it (not a native speaker)

@FreeMan thanks for the link!

No problem. Also, your English seems to be very good. I made a couple of minor grammatical changes on word order/tense that seem to be difficult for nearly all non-native English speakers.

747 domestic comes to my mind. That's a large plane with high density with short range.

If you want to go further range on a flight, cram more passengers into your plane, because that way you can make more profit

A big part of the difference in range between small and large aircraft is simply mathematical. When you make a 3D object larger, area increases with the square of length while volume increases with the cube. The A320 has a wingspan of 35.8m, carries 150 (2-class), and carries 24,210L of fuel (standard). The A380 has a wingspan of 79.75m, about twice the dimensions of the A320. However, the passenger capacity increases by a factor of 4 to 644 (2-class), and the fuel capacity increases by over a factor of 10 to 320,000L. There is simply more room for fuel in a larger aircraft. Smaller aircraft may have options to carry additional fuel talks to increase range. Note that this trend also applies to business jets despite their market having less of a correlation between range and passenger demand.
In addition to the geometrical constraints, airlines have other reasons for not operating large planes on short routes, or vice versa, more often. Using small planes allows for more frequent service and more flexibility even if there is enough demand to use a smaller number of larger aircraft.

There are five points that need to be addressed on the graph of range vs capacity, not just two.

Short and thin.  These routes are flown by small aircraft such as puddlejumpers and regional jets as well as smaller mainline aircraft, and represent the spokes in the classical hub-and-spoke model (Savannah-Atlanta or Bordeaux-Paris for instance).  Service frequencies are low to modest, and competition is generally fairly limited, with one or a few carriers on the route.
Short and fat.  These routes mainly exist in areas where there are large cities close together, but land/sea connectivity has a tough time competing due to geographical or political issues.  Examples of this include Tokyo-Osaka and Taiwan-Hong Kong.  Oftentimes, service frequencies are high, competition is fierce, and both narrowbody and densely configured widebody (2-class seating at best) aircraft can be found.
Long and fat.  These are your classical, long-haul hub-to-hub routes such as London-New York or Los Angeles-Sydney.  Most of these flights are on traditional 3-class or 4-class configured widebody aircraft, and see relatively infrequent service compared to shorter routes.
Long and thin.  These routes are introduced to relieve congestion from major hubs, usually in international markets.  An example would be Newark-Glasgow, bypassing the otherwise-obligatory plane change at Heathrow or Amsterdam.  Other examples of this pattern include US domestic long-hauls.
In the middle.  Most short-to-intermediate haul mainline flying is this way -- these may be busy hub-to-spoke connections, or inter-hub flights that aren't fat enough or long enough to sustain the use of larger aircraft.  LCC networks (Southwest, JetBlue, Ryanair, Easyjet) center around these types of routes because they work well for a homogenous fleet (vs. hub and spoke networks, which require smaller planes for the spokes and bigger planes for hub-to-hub).

Basically the airlines need keep their planes always flying, parking them idle on the airport just costs money. Parking a big plane and waiting a complete day until it gets full with passengers is expensive, flying a small plane a long time while passengers already waiting for the next flight is lost money.
In the past big planes were build for short and medium-routes, like the B747-100SR/300-SR or the A300 (first time two aisles one a twin-engine?). The 747-SR was used a lot inside Japan, while the A300 founds it first customers inside USA. But the airlines don't buy them anymore.
Consider that on short routes you are often connecting smaller airports with fewer passengers per trip, therefore a smaller plane is more efficient. On the other side, most jet-engines become more efficient when they are bigger, furthermore long boarding times are not a problem on long distance flights.
Also, one, two or three flights during a day on long routes are okay for passengers on long routes (selecting a round about departure/arrival), while on short routes you may need a flight every hour (selecting exact departure/arrival).
Notable exceptions are current B737-700ER and A319LR, both can fly around 10.000 km. I don't know the sales figures, but I think only customers with special needs buy them.

There are two design reasons for this:

Airline routes

In the hub-and-spoke system most large airlines use, larger volumes of passengers are concentrated into a few airport hubs then moved greater distances between hubs. In that system, there is little need for long distance/small passenger aircraft.

Fuel Capacity

A larger plane can carry more fuel and thus go farther. Yes, you can get a 737 configured for business that can go as far as an early 747 but, when loaded like that, it cannot carry very many people. A BBJ 737 with full fuel can only carry about 2500 lbs—about 15 passengers with no bags, no food, no nothing.

In general as an aircraft gets bigger, with more passengers, the bigger the wing has to be to carry all of that extra load. As the wing gets longer, the root has to increase in thickness quite a bit due to the increased bending moment (also due to the increased load going into the wing). As the wingspan gets longer, the wing chord usually increases at the root as well (on commercial aircraft). Finally, since the wing root has has gotten thicker and longer, the center wing under the fuselage has also gotten taller and longer.
Considering the vast majority of fuel is stored in the wings and center wing on commercial aircraft (on many that is the only location of storage), and nearly all of the wing between the spars is dedicated to fuel storage, a higher capacity aircraft just has far more fuel storage volume available.
Of course you could put a huge wing on a small aircraft to give it a lot of range, but I think the other answers have done a good job of explaining why that isn't done.

authors: Cтанислав Калин


text:
Why is the black box still relevant?
Wouldn't it be cheaper to replace black boxes by telemetry?
Seems that the costs of a single search mission for an underwater black box exceeds the cost of installing and maintaining telemetry sytem in an entire fleet of aircraft plus ground stations.
By telemetry I mean a system that broadcasts all the information instead of recording it in the black box. In case of a crash the data would be immediately available.
Wouldn't such a method have shed light on such misteries as the missing Singapur Airlines flight?
Of course, in very extreme cases where the telemetry system fails before the crash the black box would still be available as a backup.

It is mainly the amount of data that you want to have and that you do not want to rely on failing wireless communication lines. In addition you have the shear amount of data generated during flight. A single 787 generates half a terabyte of data in just a single flight:
http://www.computerworlduk.com/news/data/boeing-787s-create-half-terabyte-of-data-per-flight-says-virgin-atlantic-3433595/
You will have to transfer this via very expensive satellite connections to a ground station.

In addition and the most relevant argument against ommiting the black box is that it is very unlikely that a plane will crash but every plane in the air has to upload all of it's data for the very rare case that it crashes. It is simply cheaper to search for those very few black boxes that end up on the ocean floor. Most crashes happen during landing anyway so they can be easily recovered.

"Seems that the costs of a single search mission for an underwater black box exceeds the cost of installing and maintaining telemetry system in an entire fleet of aircraft plus ground stations."   Nope.

@Brilsmurfffje: "It is simply cheaper to search for those very few black boxes that end up on the ocean floor". I'd be interested in the figures you use. The localization of AF447 and MH370 recorders are not expensive, the cost is actually huge. The next generation of ATC will include the use of ADS-B satellites to prevent that, and allow other savings and improvements.

To add to what others have said, your question assumes that if we know all the details on why a plane crashed we wouldn't spend any money on finding the wreckage.  Yet the wreckage can yield valuable information on how, when, and why a plane broke up.


text:
Why do Ryanair not use jetways?
Whilst flying into London's Stanstead Airport the other day I noticed that despite there being many jetways available Ryanair weren't using them for any of their planes. Instead, they'd chosen to have pairs of staircases at either end of the plane. The same is also true when they are operating out of other airports where jetways are available.
Is this just done for speed or might there be other reasons for making this decision?

This article seems to confirm your hypothesis, but also suggests that airports charge more for using jetbridges. I've also noticed that some (all?) Ryanair aircraft have airstairs for the front door, which they deploy as quickly as possible, precluding the use of a jetbridge. http://www.traveller.com.au/ryanair-slashes-flights-after-row-over-stairs-1d3ie

I vote to re-open this question. The other question is about airlines in general. This one is about Ryanair, and the answer, like the answer to most questions about Ryanair, is "To humiliate their passengers." Anyone who has watched successive Ryanair flights disgorge their human cargo down slippery wet steps in driving, freezing rain and oblige them to walk across puddled tarmac with the wind raising huge sheets of water into the air, before doing the same in reverse to a fresh load of victims, will sense the truth of this.

I too really don't feel this is a duplicate of another question. The "duplicate" asks who decides where a plane gets put, mine asks a question about why a particular airline makes the descision to nevwr use jetways for their flights.


text:
How much testing to commerical aircraft manufacturers typically do on each new plane after it rolls off the production line?
I just came across an article on Wired about Boeing's new 787-10 where they said the type had been tested for over 5000 hours in a range of conditions.
Obviously, the very first model is tested to extremes but when full scale production starts what kind of testing is typically done on each individual plane ?

Related: What is a Certification Flight?

Testing is performed for specific reasons.  As you noted testing for certification and testing production aircraft are not the same.
Testing for certification is to establish that the design of the aircraft meets airworthiness standards. A guide is available in the form of AC 25-7C.
Testing production aircraft is primarily a quality control issue and serves to prove that the aircraft is built to the drawings -- that it complies with the approved design.  It's only a small part of the process and is discussed in section 2.7 of AC 21-43A.
As noted, in the AC a flight test is required (with one exception). Production testing will evolve over time as there is a constant effort to 1. ensure adequate test coverage to avoid quality 'escapes' and 2. to do it as efficiently as possible to minimize costs.
One other test that is typically performed is an acceptance test. This is not regulatory. It is contractual and is performed with the participation of the customer.  Airlines won't accept delivery of an aircraft until they're satisfied it meets everything they're paying for. A friend of mine who worked for an airline's engineering group said it was about a 4 or 5 day process to checkout and accept delivery of a plane.

That depends upon how long the plane has been in production. By the time an aircraft has been in production for a while, there is usually only one flight test (in addition to testing on the ground).
When the first production model comes of the line, it gets a lot of testing. Then there is a list of problems identified. Subsequent tests will focus on those problems.
Thus, you switch from trying many things to see if a problem occurs to trying specific things to see if specific problems occur.

Anything to back this up?


text:
How can pilots obtain runway length information for airports that do not appear in the chart supplement?
How can pilots obtain official runway length information for airports that do not appear in the chart supplement such as private airports?

A lot of private airports, as long as they appear on a chart will also appear in the chart supplement. Otherwise you'd have to call the airport operator (which you would need permission from anyway to land there). Do you have an example of an airport that is on a chart, but not in the supplement?

Horseshoe Acres, and Brady east of lake Okeechobee in FL

You can't obtain official runway length information, if you could they'd be in the chart supplement.

If an airport does not appear in the Chart Supplement, the only official information about it seems to be in the relevant Sectional Chart.
In the case of Horseshoe Acres (FA24), the sectional shows that the longest (and only) hard-surface runway is "18", which means 1770 to 1869 feet.
In the case of Brady Ranch (80FD), the sectional shows that the longest (and only) hard-surface runway is "46", which means 4570 to 4669 feet.
Note that you can only guess the runway numbers, the lengths of shorter runways, and the presence of unpaved runways. As @RonBeyer comments, since you have to get permission to land on these fields anyway, it's probably best to ask for such details at the same time. If you get data from the airport operators themselves, that would seem to qualify as official.
However, Airnav and others have lots of consistent data about many airports not in the Chart Supplement, particularly private ones, so it's possible there is some other common source. Since I don't know what that might be, I can't guess how official it is.

Just use the ruler feature for measuring distances down to feet in Google Earth.  Not "official" but pretty accurate.

For emergency,yes. But not for normal operation. You have no idea when is the last time google update their maps. The airport may not even be there.


text:
On the ICAO Flight Plan Form, does /S replace O, V, and L?
I know the S stands for standard equipment (VOR, ILS, VHF radio).
Is the format like G/S (GPS with standard equipment), or does the /S not imply coverage of the other line items, i.e., VLGO/S?

I wanted to address your formatting first since equipment type identifiers come before the transponder identifier (i.e. before the slant). The format for the new ICAO Domestic flight plan form for item 10 (equipment) is as follows:
(equipment type letters) / (transponder type)
So as an example, if your aircraft has standard equipment, VOR, GPS (GNSS), DME and you were Mode C Transponder equipped, your entry for item 10 would look like this:
SGD / C
*notice that your equipment type doesn't include "O" for VOR since S also includes VOR.
To answer your concrete question, S does indicate the presence of O, V, and L.
I've attached the following tables from 5-1-21 and 5-1-22 in the AIM for your reference. Table 5-1-4 covers equipment letter identifiers and table 5-1-5 covers transponder letter identifiers.

I called a briefer and got an answer the other day.  This answer is correct.


text:
Is there an increased concern for stall safety in a 1G steep turn?
Most people know the standard, "At a 60 degree bank, an aircraft experiences 2G's" checkpoint for load-factor on an airplane.
I assume that this statement has an underlying, unspoken assumption that the aircraft is maintaining a constant altitude in the bank.
This leads on to matters of increased stall speed during turns.
My question is, if no pitch adjustment is made while in a coordinated turn, which I think means that no additional load-factor is acting on the aircraft, is the stall speed still affected?

Note that to maintain 1G in a turn you must be not only descending but accelerating downward.

@pericynthion good point.

To fly a 60-degree bank coordinated turn with 1 G on the aircraft, you'll be dropping like a rock.
But your stall speed with 1 G on the aircraft is what it is, regardless of how you obtain that 1 G -- straight & level, or coordinated turn with deceleration down to reduce the G loading, or inverted & pulling 1 G... the angle of attack that stalls your wing will be reached at the same speed in all of those cases.

That aircraft is accelerating at 50% rate compared to the rock, because the fraction of the lift that remains to counter gravity is cos 60° = 1/2. Otherwise fully agree!


text:
What is an obstacle identification surface and why would a pilot intentionally penetrate it during an ILS approach?
What is an obstacle identification surface?
Why would a pilot intentionally penetrate it during an ILS approach?

Obstacle Identification Surfaces apply to departures and the portion of an non-precision IAP beyond the Visual Descent Point. If you are in the clouds, you should never penetrate the OIS on departure.
On arrival, the VDP assures obstacle clearance with a normal approach to landing. ILS only approaches do not have a VDP depicted so there is no OIS to penetrate. (The glide slope takes you right to the touchdown zone.) ILS/LOC (and Localizer only) approaches do have a VDP for the non-precision version of the approach. You could penetrate the OIC on a localizer approach and if that happens, visibility minimums are increased as explained in the last paragraph from the AIM below.
AC 150-5300-13-c12 Airport Design has a good visualization of the departure OIC.
(As an aside, it has lots of charts and graphs showing how departures and approaches are designed.)

AIM 5−2−8. Instrument Departure Procedures (DP) − Obstacle Departure Procedures (ODP) and Standard Instrument Departures (SID)

…if an obstacle penetrates what is called the 40:1 obstacle
identification surface, then the procedure designer chooses whether
to:

Establish a steeper than normal climb gradient; or

Establish a steeper than normal climb gradient with an alternative that increases takeoff minima to allow the pilot to visually remain
clear of the obstacle( s); or

Design and publish a specific departure route; or

A combination or all of the above.

The 40:1 obstacle identification surface (OIS) begins at the departure end of runway (DER) and slopes upward at 152 FPNM until
reaching the minimum IFR altitude or entering the en route structure.
This assessment area is limited to 25 NM from the airport in
nonmountainous areas and 46 NM in designated mountainous areas. Beyond
this distance, the pilot is responsible for obstacle clearance if not
operating on a published route, if below (having not reached) the MEA
or MOCA of a published route, or an ATC assigned altitude. See FIG
5−2−1. (Ref 14 CFR 91.177 for further information on en route
altitudes.)

5−4−5. Instrument Approach Procedure (IAP) Charts

h. The Visual Descent Point (VDP), identified by the symbol (V), is a
defined point on the final approach course of a nonprecision
straight−in approach procedure from which a stabilized visual descent
from the MDA to the runway touchdown point may be commenced. The pilot
should not descend below the MDA prior to reaching the VDP.
i. A visual segment obstruction evaluation is accomplished during
procedure design on all IAPs. Obstacles (both lighted and unlighted)
are allowed to penetrate the visual segment obstacle identification
surfaces. Identified obstacle penetrations may cause restrictions to
instrument approach operations which may include an increased approach
visibility requirement, not publishing a VDP, and/or prohibiting night
instrument operations to the runway. There is no implicit obstacle
protection from the MDA/DA to the touchdown point. Accordingly, it is
the responsibility of the pilot to visually acquire and avoid
obstacles below the MDA/DA during transition to landing.

Edit: This AIM is consistent with what the Instrument Procedures Handbook says about non-precision approaches but not consistent with what the handbook says about the potential for obstacles on ILS approaches.
p 7-9

...if an ILS is configured with approach lights or a nonprecision
approach is configured with either MALSR, SSALR,or ALSF-1 lighting
configurations and the procedure has a published visibility of 3/4 SM
or greater, a penetration of the final approach OIS may exist. Also,
pilots will be unable to determine whether there are penetrations of
the final approach OIS if a nonprecision procedure does not have
approach lights, or is configured with ODALS,MALS, or SSALS/SALS
lighting since the minimum published visibility will be 3/4SM or
greater.
As a rule of thumb, approaches with published
visibilities of 3/4SM or more should be regarded as having final
approach OIS penetrations and care must be taken to avoid any
obstacles in the visual segment. Approaches with published
visibilities of 1/2 SM or less are free of OIS penetrations...

Verbatim knowledge test question: "How can the pilot determine, for an ILS runway equipped with MALSR, that there may be a penetration of the obstacle identification surfaces (OIS), and care should be taken in the visual segment to avoid any obstacles?" This conflicts with your statement that it doesn't apply to ILS.

@RyanMortensen I am quoting directly from the AIM and noting that I cannot find any ILS only approaches with a VDP. In my judgement, around 5% of the Knowledge Test questions are either wrong or misleading or have contradictory answers. This appears to be one. I made an edit to reflect what they want on the test.

I agree that this addition completes the answer.  I would like to note for others' reference that a 1:40 rise/run or 152Ft per NM rise is a 1.43 degree slope angle.  Well below the standard 3.0 glide slope.

I think the key statement from your entire answer is, "There is no implicit obstacle protection from the MDA/DA to the touchdown point."

I'd also like to add that 152ft/NM is only the obstacle ID surface, not the expected standard minimum climb gradient of 200ft/NM giving a clearance gain of 48ft/NM. And added to that, the OIS starts way out at the tippy end while the standard climbs/descents intersect the 35ft threshold crossing height or landing zone.

For vertically guided approaches between DA and threshold see "vertical guidance surface" VGS FAA order 8260.3D (was called GQS in 8260.3B, changed in .3C without explanation) it is a surface that ensures no maneuvering around obstacles will be needed for straight-in approaches, it is allowed to be penetrated by some frangible equipment required for operations like radar reflectors and approach lights. Wheel crossing height is considered for the size-category of aircraft to be served. It seems VGS is also being applied to some non-precision approaches now.


text:
Why are Oscar, India, and X-Ray (O, I, and X) not used as taxiway identifiers?
An old CAR "Licensing of Aerodromes" document indicated that taxiways may not be designated by O, I, or X.
Is this still in effect today?  Why were (or are) those not used as taxiway identifiers?
My guess is that the shapes of those letters could cause confusion such as an "X" meaning something like "closed" or I looking like a vertical line "|".

The 1990 Wayne County Airport runway collision happened because they missed the turn onto taxiway "Oscar 6", and again when instructed to turn onto XRay but instead turned onto Runway 03C. I believe DTW renamed the runways/taxiways after this (but not sure if one correlates the other) because there is no longer a taxiway "O6", "X" or a runway 03C.

@RonBeyer that airport is known to most people as "Detroit Metro", DTW, or just  "Detroit", where it would be perfectly normal for two jetliners to be.  There is another major airport in Wayne County that is airline-capable, but it is GA only.  When you don't use Metro/DTW by one of its proper names, people might think you mean the other...

@Harper That's the title of the Wikipedia article I linked to, which is why I used it. I personally refer to it as DTW (and did so in my post), so there shouldn't be any confusion about what airport I'm referring to.

That page is amazingly sparse. I assume the 727 was able to successfully take off before returning, given the relatively small amount of damage for such an awful situation.

@zymhan: According to the accident report (PDF), the captain "rejected the takeoff and stopped the airplane using maximum braking."

Because those symbols are easily confused with the number 0, the number 1 and the symbol for a closed runway/taxiway (✕) respectively.

(1) Numbers  by  themselves,  and  the  letters  "I"  and  "O"  must  not  be  used  because  they could be mistaken for a runway number.
(2) The letter "X" must not be used because a sign with an "X" could be misconstrued as indicating a closed taxiway or runway.

Source: FAA Engineering Brief No. 89 on Taxiway Nomenclature Convention (via SKYbrary.aero).
Most aerodromes do refrain from using these identifiers, but there are also examples of them being used. For example, Copenhagen (EKCH) has a taxiway I(ndia).

Interesting.  Nice catch

@ymb1 Thanks! Was looking for an ICAO reference, but stumbled upon the FAA document first :)

"X" marks a closed runway or an airstrip where aircraft may not land.  See this temporary marker as an example of how it is used.

I have tow-launched hang gliders from an old WWII airstrip in Suffolk (England), which was shared with microlight pilots.  We had one of these markers which we laid out before flying, to prevent other aircraft from inadvertently landing there whilst we were towing.


text:
Does the mixture and throttle setting affect the quality of priming of fuel prior to start?
This question is a generality.  For airplanes with small reciprocating engines, does the mixture and throttle setting at the time of priming affect the quality of the priming or the engine start, or is the priming unaffected by mixture and throttle positions?
Does it make a difference if the engine has carburetor or fuel-injected in regards to mixture and throttle at priming time?

Related

On a carbureted engine, the mixture and throttle setting does not affect prime, which uses a separate injection system that draws fuel into a syringe and injects it into the intake passages at the cylinders when you push in the primer's syringe plunger.
On a fuel injected engine, where the Bendix mechanical fuel injection system is pretty common, if the fuel system is pressurized and the mixture is rich, the system is injecting sufficient fuel at each cylinder for idle continuously.  So you prime them by doing just that, pressurizing and advancing mixture, for a set period of time, say, 3 seconds or whatever, then pulling the mixture back to idle cutoff to stop spraying gas.  This does the same thing as stroking the primer on a carb engine.  Like the carb engine, it doesn't matter where the throttle is at this point.
When you start an injected engine, you start with the throttle cracked like a carb engine, but unlike a carb engine where you put the mixture to rich for the start, you have to crank with mixture at idle cutoff and move the mixture forward after the engine fires before it consumes the fuel vapour in the intake passages created by priming, within a second or two.
Injected engines are more finicky to start because the amount of prime is a bit harder to regulate, being a timing function that you have to adjust for ambient temps and engine warmup state vs counting primer strokes so they are much easier to over/under prime, and as well the timing of the advancement of the mixture after start is important.  Do it too soon and you can get flooding or intake backfires and too late it dies before it really gets going.

Only a bit related, but the carbureted Lyc on my airplane was set (by the previous owner) with the idle mixture leaner than normal. I realized this when I noticed there was no rpm blip when you selected idle cutoff, and it explained why the thing was hard to keep running when cold even with adequate prime.  This was done to minimize lead fouling running avgas.  I use mogas but have never bothered to re-adjust it.  It means though that if it's cold out, I start with the primer plunger extended, and slowly feed in prime after it catches.  After about 10-15 seconds it isn't necessary any more.


text:
Why is a small amount of smooth ice over the top of the wing more dangerous than an accumulation on the leading edge?
According to a Gleim study guide,

"Generally speaking, smooth ice on top of the wing is more dangerous than heavy accumulated icing on the leading edge."

Is this true? If this is true, why?

Wings are designed with very specific shapes, and adding ice throws it off. Not only is the flow messed up, but it also makes it difficult for spoilers and other flaps to work. With ice on the leading edge only, I would assume the slats would still function and while the flow would be affected, it should still stay on the wing as designed. Plus, there's the issue of evacuation and such, where ice on the wing is a slipping hazard (but at this point it's the least of everyone's concerns).

Make that an answer and I will upvote it.  Also, clear ice adds a lot more weight than rime.

@Pheric I vaguely remember read in some place Fokker 100 was particularly prone to problems with ice formation in their thin short wings but cannot find a reference and it caused a couple of crashes but cannot find a reliable reference

This seems to be from an older Gleim study guide.  It references a now-cancelled AC 91-51A:

(AC 91-51A) Ice on the leading edge, while seemingly more dangerous, can be removed using deicing systems. Ice on the upper surface is much more difficult to clear from the structure, thus making it more dangerous.

This AC has been replaced by 91-74B, which repeatedly mentions the dangers of ice on nonprotected surfaces, but also points out that:

Ice on an airfoil can have other effects not depicted in these curves. Even before airfoil stall, there can be changes in the pressure over the airfoil that may affect a control surface at the trailing edge.

and, discussing roll upsets:

If the flaps are extended, do not retract them unless it can be determined that the upper surface of the airfoil is clear of ice. Retracting the flaps will increase the AOA at a given airspeed.

So current guidance seems to be that ice on the upper surface of the wing is dangerous because of:

The upper surface of the wing generally not featuring an ice protection/removal system, and
The possibility of control surfaces being affected.

but it doesn't go so far as to say it is "more" dangerous.